feat: Add SQLite database support and fixed portable extraction path

- Add SQLite as alternative database for offline/firewall environments
- Add --database-type parameter to build-client.bat (mysql/sqlite)
- Refactor database.py to support both MySQL and SQLite
- Add DB_TYPE and SQLITE_PATH configuration options
- Set fixed unpackDirName for portable exe (Meeting-Assistant)
- Update DEPLOYMENT.md with SQLite mode documentation

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/app/config.py

@@ -21,6 +21,8 @@ class Settings:
     BACKEND_PORT: int = int(os.getenv("BACKEND_PORT", "8000"))
 
     # Database Configuration
+    DB_TYPE: str = os.getenv("DB_TYPE", "mysql")  # "mysql" or "sqlite"
+    SQLITE_PATH: str = os.getenv("SQLITE_PATH", "data/meeting.db")
     DB_HOST: str = os.getenv("DB_HOST", "mysql.theaken.com")
     DB_PORT: int = int(os.getenv("DB_PORT", "33306"))
     DB_USER: str = os.getenv("DB_USER", "A060")
@@ -90,6 +92,21 @@ class Settings:
             return os.path.join(base_dir, self.RECORD_DIR)
         return os.path.join(base_dir, "record")
 
+    def get_sqlite_path(self, base_dir: str | None = None) -> str:
+        """Get SQLite database file path, resolving relative paths.
+
+        Args:
+            base_dir: Base directory for relative paths. If None, uses get_base_dir()
+                     which supports frozen executables.
+        """
+        if base_dir is None:
+            base_dir = get_base_dir()
+        if self.SQLITE_PATH:
+            if os.path.isabs(self.SQLITE_PATH):
+                return self.SQLITE_PATH
+            return os.path.join(base_dir, self.SQLITE_PATH)
+        return os.path.join(base_dir, "data", "meeting.db")
+
     # Timeout helpers (convert ms to seconds for httpx)
     @property
     def upload_timeout_seconds(self) -> float: